/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.io.hfile;

import java.io.DataOutputStream;
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.ExtendedCell;
import org.apache.hadoop.hbase.io.encoding.DataBlockEncoding;
import org.apache.hadoop.hbase.io.encoding.HFileBlockDecodingContext;
import org.apache.hadoop.hbase.io.encoding.HFileBlockEncodingContext;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * Controls what kind of data block encoding is used. If data block encoding is not set or the given
 * block is not a data block (encoded or not), methods should just return the unmodified block.
 */
@InterfaceAudience.Private
public interface HFileDataBlockEncoder {
  /** Type of encoding used for data blocks in HFile. Stored in file info. */
  byte[] DATA_BLOCK_ENCODING = Bytes.toBytes("DATA_BLOCK_ENCODING");

  /**
   * Starts encoding for a block of KeyValues. Call
   * {@link #endBlockEncoding(HFileBlockEncodingContext, DataOutputStream, byte[], BlockType)} to
   * finish encoding of a block.
   */
  void startBlockEncoding(HFileBlockEncodingContext encodingCtx, DataOutputStream out)
    throws IOException;

  /**
   * Encodes a KeyValue.
   */
  void encode(ExtendedCell cell, HFileBlockEncodingContext encodingCtx, DataOutputStream out)
    throws IOException;

  /**
   * Ends encoding for a block of KeyValues. Gives a chance for the encoder to do the finishing
   * stuff for the encoded block. It must be called at the end of block encoding.
   */
  void endBlockEncoding(HFileBlockEncodingContext encodingCtx, DataOutputStream out,
    byte[] uncompressedBytesWithHeader, BlockType blockType) throws IOException;

  /**
   * Decides whether we should use a scanner over encoded blocks.
   * @return Whether to use encoded scanner.
   */
  boolean useEncodedScanner();

  /**
   * Save metadata in HFile which will be written to disk
   * @param writer writer for a given HFile
   * @exception IOException on disk problems
   */
  void saveMetadata(HFile.Writer writer) throws IOException;

  /** Returns the data block encoding */
  DataBlockEncoding getDataBlockEncoding();

  /**
   * @return the effective in-cache data block encoding, taking into account whether we are doing a
   *         compaction.
   */
  public DataBlockEncoding getEffectiveEncodingInCache(boolean isCompaction);

  /**
   * Create an encoder specific encoding context object for writing. And the encoding context should
   * also perform compression if compressionAlgorithm is valid.
   * @param conf        store configuration
   * @param headerBytes header bytes
   * @param fileContext HFile meta data
   * @return a new {@link HFileBlockEncodingContext} object
   */
  HFileBlockEncodingContext newDataBlockEncodingContext(Configuration conf, byte[] headerBytes,
    HFileContext fileContext);

  /**
   * create a encoder specific decoding context for reading. And the decoding context should also do
   * decompression if compressionAlgorithm is valid.
   * @param conf        store configuration
   * @param fileContext - HFile meta data
   * @return a new {@link HFileBlockDecodingContext} object
   */
  HFileBlockDecodingContext newDataBlockDecodingContext(Configuration conf,
    HFileContext fileContext);
}
